This Vienna bridge multi-band oscillator circuit was found in a 1974 Ferranti transistor manual. The circuit generates signals from 25 Hz to 1 MHz in 5 bands selected by the capacitors.
This is an old test circuit for integrated TTL counters, feeding a Nixie tube, common at the time....
This old oscillator using germanium transistors has a high impedance headphone as inductor to...
This preamp with several inputs using germanium transistors from the time was found in Japanese...